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8 minutes ago, Ferdinand said:

 

What is that potential saving in cash terms per annum?

 

I can put some numbers to our electricity usage.  We pay about £50/month for electricity, including charging my car, heating and ventilating the house, and delivering hot water.  Most of that (around 70% at the moment) is at 8.148p/kWh.  The percentage of cheaper tariff electricity, if we switched to Go or Agile would decrease to around 50%, and the percentage of peak rate electricity would increase, just because we can't easily adapt usage to fit in with shorter cheap rate periods (without investing in battery storage).

 

The saving we could make from installing battery storage would be around £150 to £200/year, from a combination of better utilising PV generation (not a great benefit, as there's only really an excess when we don't use much electricity) and being able to partially take advantage of a flexible tariff.  That's nowhere near enough of a saving to justify investing in a battery system, especially as we continue to receive the FiT and export payments of ~£1000 a year.  The latter means we don't pay anything at all for energy, in reality, and we have another 14 years to go like that.

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37 minutes ago, cmorewood said:

excess solar at 6ah, 2kWh

Do you mean charging a rate of 6 A, which is around 1.4 kW (how fast you fill the batteries), or putting in 2 kWh of charge (how much you fill the batteries)?

39 minutes ago, cmorewood said:

20kWh I can't seem to get the 50 kWh ones to work with the Tesla

Same here.

One of my local Tesco has a 7.5 kW charger, would have to have a very long coffee there to make it worthwhile charging up.  But it does have a view over Carbis Bay, so not too bad.

 

42 minutes ago, cmorewood said:

I've got 40 Navitron 58mm tubes heating 350 lit in 2 tanks

Did you do a costing of putting in extra PV to just heat the water?

How much does it cost to service your ST system each year?

Generally PV is not cheaper to install than ST and is also more reliable, but if you have a good working system, that you can self service, probably not a lot in it.  Be good to know though.

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Posted (edited)
On 31/03/2020 at 15:52, Ferdinand said:

 

What is that potential saving in cash terms per annum?

When its all up and running.. a good bit.

2018 the last complete year no solar no batteries just 15 tubes for solar water heating.

Gas 14178 kWh costing £ 400 approx

Elec 3851kWh costing  £532

                                         £932 total

 

2021 expected with everything running properly smart meter, batteries and car 8000 miles per year 70% charging at home

Gas 15kWh  costing £65 approx

Elec 6500    costing £440 @ 6p overnight or solar charging

                                   £505 total

minus RHI/FIT         £1494

Profit                         £989 or over £82 pm

Of course this is just guess work.. but I have figures for the house going back 10 years when the kids were still at home so its an educated guess.

Edited by cmorewood
correct figures

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Posted (edited)
On 31/03/2020 at 16:21, SteamyTea said:

Do you mean charging a rate of 6 A, which is around 1.4 kW (how fast you fill the batteries), or putting in 2 kWh of charge (how much you fill the batteries)?

The Tesla display  gives me  readout when I charge at 5a that equates to 1kWh and when I up that to 6a it changes to 2kWh. If I'm reading it properly

 

On 31/03/2020 at 16:21, SteamyTea said:

Did you do a costing of putting in extra PV to just heat the water?

How much does it cost to service your ST system each year?

Generally PV is not cheaper to install than ST and is also more reliable, but if you have a good working system, that you can self service, probably not a lot in it.  Be good to know though.

I put the solar thermal in myself about 7 years ago. it cost just about £900 including new 150 lit tank it was initially a Navitron 20 tube 42mm system.. worked fairly well in the summer . the hot water fed into the cold water of the combi boiler and so pe heated the water for the boiler all year.. even by a couple of degres in the winter. I gradually added bits i.e 10 Navitron 58mm  tubes then another 10  and when we had the roof done last year I switched the 48mm tubes for a 58mm system.

The new system which has been up and running for about 9 months is a 40 tube Navitron, (well 38 complete tubes as I managed to break the seal on two getting them on the roof but they're still working just not as efficiently as the others) into a 200 lit double insulated copper tank which is connected to the 210 lit as a pre heat so that if the water temp goes over 70c it diverts to heating the secondary tank. That lot cost about £1200 to fit and I managed a lot of it.

ST works much better than PV I've found you seem to get more "bang for your buck"

Servicing? There is none for the ST the PV I think is about £135/yr pls mileage.. but since they're coming back to connect the batteries...

Edited by cmorewood
sp

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10 hours ago, cmorewood said:

When its all up and running.. a good bit.

2018 the last complete year no solar no batteries just 15 tubes for solar water heating.

Gas 14178 kWh costing £ 400 approx

Elec 3851kWh costing  £532

                                         £932 total

 

2021 expected with everything running properly smart meter, batteries and car 8000 miles per year 70% charging at home

Gas 15kWh  costing £65 approx

Elec 6500    costing £440 @ 6p overnight or solar charging

                                   £505 total

minus RHI/FIT         £1356

Profit                         £851 or over £70 pm

Of course this is just guess work.. but I have figures for the house going back 10 years when the kids were still at home so its an educated guess.

 

This analysis, and bits of the OP, are making me itch that it doesn't all quite hang together, and I can't quite put my finger on why. It may be that I want to see more information about details and consequences. It may be that you have thought about these aspects, but it is always better to ask.

 

- Can you explain the statement "we have achieved an A99 rating". Does that mean calculated with the new additions, or where you are with just Solar Thermal? If the latter,  then why do you think the bills are £932 a year. Mine is a 2000 sqft C75 ish rating ignoring the solar PV (ie I have not had it redone), and my bills are around the same (before the adjustment for the solar PV).

 

- Where is that RHI / FIT coming from - breakdown into PV / RHi for Solar thermal / PV would be useful?

 

(£1356 seems a heck of a lot, and I didn't know that you got RHI for Solar Thermal you had self-installed. A recent PV setup will have very little FIT payments, and after you go to Octopus Agile I think you are auto-switched to the Export Tariff Scheme instead  at approx. 5p / unit. I have a 10kWp solar installation and at 11p per generated unit ish I get between £500 and £600 a year benefit plus self--use.

 

TBH to me that is not realistic as a real world number.)

 

- What assumptions are you making about how much of the solar you  will use yourselves?

 

- Are you comfortable going for the Agile Tariff which is subject to short term change, instead of FIT with a 20 year guarantee? How do you know you won't be shafted next year? 

 

- On a like for like basis on these calcs your "profit" is actually 427 +  1356 = £1783 pa. Seems a lot.

 

- Have you done calculations for each sub-project to see whether they are all worthwile?

 

- I think some ROI numbers would help,  which could be as simple as Payback if you make appropriate assumptions on inflation etc. Although NPV would be better.

 

Ferdinand

 

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Posted (edited)
On 01/04/2020 at 12:09, Ferdinand said:

 

- Can you explain the statement "we have achieved an A99 rating". Does that mean calculated with the new additions, or where you are with just Solar Thermal? If the latter,  then why do you think the bills are £932 a year. Mine is a 2000 sqft C75 ish rating ignoring the solar PV (ie I have not had it redone), and my bills are around the same (before the adjustment for the solar PV).

 

The Energy Performance Certificate A99 rating was issued in November last year with all the additions we have done, adding insulation (as part of the refurb), ASHP, solar thermal and PV . The figures I have there are for 2018, the last full year I could make a comparison as the house has totally changed since then.

 

On 01/04/2020 at 12:09, Ferdinand said:

 

- Where is that RHI / FIT coming from - breakdown into PV / RHi for Solar thermal / PV would be useful?

£180/yr     FIT for PV min estimate as I'm still awaiting payment, they had a problem with a line diagram and didn't contact me.

£428/yr RHI for ST minimum estimate as they haven't paid me yet due to a mix up in MCS. The initial setup was self installed but when they installed the HP they added the 58mm tubes and tank and comissioned it as a new installation which in effect it was.

£886/yr     RHI for ASHP

On 01/04/2020 at 12:09, Ferdinand said:

 

- Are you comfortable going for the Agile Tariff which is subject to short term change, instead of FIT with a 20 year guarantee? How do you know you won't be shafted next year? 

I don't think you "have" to go on to the Agile export tariff. From what I read it was brought in to give those who had no access to FIT i.e had installed PV after the cutoff date of April last year some reward for exported electicity. As far as I'm concerned I stay on the FIT agreement I have with SSE.

On 01/04/2020 at 12:09, Ferdinand said:

What assumptions are you making about how much of the solar you  will use yourselves?

We will be using as much as we can for battery charging and car charging. But it doesn't really matter as FIT pays you whether you use it or export it.

 

On 01/04/2020 at 12:09, Ferdinand said:

- On a like for like basis on these calcs your "profit" is actually 427 +  1356 = £1783 pa. Seems a lot.

Of course the profit is not actually profit per say, it covers the EST 0% loan we took out to install the ASHP.

I can't calculate things on a like for like basis as the house has changed so much and the money we have spent on the house will probably take 10 plus years to recover especially given the global rescession after the COVID19 outbreak has settled.

On 01/04/2020 at 12:09, Ferdinand said:

- Have you done calculations for each sub-project to see whether they are all worthwile?

Each sub- project was costed and should begin payback after approx 5yrs Batteries (after they're all connected) 3yrs ST, 7 yrs ASHP, and 11 yrs PV (although the 1st year has outperformed the projected generation figures by 18%)

I keep my cars for about 20 years so if the Tesla lasts that long at 4p per mile and 200 000 miles ish I think that will pay for its self as well.

But in the end they are all worthwhile as I will be using less energy that I was 2 years ago and doing my bit to save the planet and that is the most important thing to me.

 

Wow this is some welcome thread!!

Edited by cmorewood
correct figures

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Posted (edited)

On batteries - we have a 10kWh LG DC battery (originally ordered a Tesla AC battery, but that caused a problem because of the limit set by Western Power). Over 2019 we used 4.95MWh of our solar power, of which 2.25 came via the battery. We are on the lowest feedin tariff as we only just made it before the cut-off, so we save in the order of 10-12p per kWh by avoiding the roundtrip to the grid for those 2250kWh. I can see that a little more capacity, such as the 13kWh offered by Tesla would be optimum, and that's about where some research I read put it for the normal domestic situation. We're switching to a variable tariff this year so I hope we'll be able to time-shift the cheaper power then. Even at the crappy feed-in rate our net electricity cost was zero (we are all electric, including borehole water and sewage treatment pant, so that's the only utility bill). In the summer quarter we were asked by the electric company to provide photos of our feed-in meter to prove we were telling the truth about how high it was, and by another part of the same company to check our readings on the consumption side because they were so low!

 

Edited by Eileen
Being more pedantic over units!!!

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18 minutes ago, cmorewood said:

Wow this is some welcome thread!!

well you started by introducing yourself and your project.

The rest is 'thread drift', which in this case, is good.

We like people that have data as it makes life clearer.

Now are you going to explain to @Eileen the proper way to show units.

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And all I wanted to ask is "Does anyone have a Samsung ASHP?" 🤣🤣

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We have a Daikin!

 

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No doubt a quirk of the low energy consumption in these troubled times, but Octopus actually charging a negative rate for  electricity this afternoon.

 

Mind you the peak rate of nearly 20p later on is what kills this for me.

 

3434549.jpg

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28 minutes ago, ProDave said:

No doubt a quirk of the low energy consumption in these troubled times, but Octopus actually charging a negative rate for  electricity this afternoon.

 

Mind you the peak rate of nearly 20p later on is what kills this for me.

 

 

I read a post on another forum by a character saying that he'd hooked up a load of electric heaters in the garden so that he could earn more money from negative pricing. . .

 

The peak rate kills it for us, too, as does the normally slightly higher rate over the whole overnight period.  Moot point, anyway, as with no mobile signal we couldn't have a smart meter even if we wanted one.

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Depending on the contract that Agile has with the generation operators, it is probably cheaper to let your customers put fan heaters in the garden than ask the wind and solar farm operator to turn the facility off.

They are probably paying more than 3p/kWh to buy the power in, but would possibly be paying 5p/kWh if they did not take the power.

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